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Help! Marshall 2210 mains fuse blowing

jon9

Member
Joined
Mar 9, 2005
Messages
243
I have a Marshall model 2210 from 1986. One day I was checking something and I had the chassis out of the box and turned upside down sitting on my speaker cab. Well, I unplugged the guitar (amp was on But I think I had it on standby) and tossed the cord onto or should I say into the amp chassis. I know what an idiot. As it was in mid-air my brain was thinking the same thing but the hands didn't react. Anyway, it popped the fuse so I put a new one in and it blows it when it goes off standby so of course I went through about 5 more fuses(because I didn't want it to be anything else, of course) but the amp goes on everything heats up fine but as soon as you click it off standby, Blows the fuse and the room lights flicker(spooky). It's not the tubes I've checked them and nothing seemed to get obviously fried (no fire, smoke or smell) So does anyone have a clue of what it could be and how to test for that. Below I've included the schematics. Thanks so much--john


Power Amp Section

Pre Amp Section
 
Last edited:

sickboy79

New member
Joined
Apr 2, 2002
Messages
5,161
acorkos said:
take all the tubes out and then turn it on....fuse still blowing?

Exactly, check the power tubes first. I had this happen to me once and it turned out to be a bad power tube.
 

jon9

Member
Joined
Mar 9, 2005
Messages
243
acorkos said:
take all the tubes out and then turn it on....fuse still blowing?

Yes, It still blows the fuse with the tubes out.
 

Buffaloe

All Access/Backstage Pass
Joined
Jul 15, 2001
Messages
4,431
I had this happen once on a head that had gotten drowned. Turned out to be a shorted power tranny.
 

NewOldCokeDave

Active member
Joined
Jul 16, 2001
Messages
4,944
Something else to look at is seeing as the cord flew into the chassis, check to see that something didn't get bent and is now grounded out by the impact of the cord tip.
 

jon9

Member
Joined
Mar 9, 2005
Messages
243
NewOldCokeDave said:
Something else to look at is seeing as the cord flew into the chassis, check to see that something didn't get bent and is now grounded out by the impact of the cord tip.

No, That was the first thing I checked. Thanks!
 

JoeV

New member
Joined
Mar 14, 2006
Messages
598
You have a dead short in the B+ supply somewhere. Likely you blew out a component or two (caps most likely) with excessive current when the plug bridged the B+ to ground. I'd be surprised if you blew the tranny, since the fuse popped and supposedly did its job.

BTW, an open chassis with the amp plugged in IS NOT safe just because it's on standby. You still have wall voltage live all the way to the switch.

Take it in to a good tech.
 

jon9

Member
Joined
Mar 9, 2005
Messages
243
Thanks for the advice, I know the danger of what's inside these amps, and of course I know I could take it to a good tech, It's just one of many amps I have to get working properly and I also need to re-tube 3 amps so I would like to save a little money if possible and I would like to fix it myself. That's why I ask the question here.
 

jon9

Member
Joined
Mar 9, 2005
Messages
243
In case anyone cares. It was the rectifier diodes. I replaced them and it's fixed. Thanks for your help.
 

ronaldurban

Les Paul Froum Member
Joined
Apr 19, 2005
Messages
318
acorkos said:
the best advice, at this point
One time I was f'n trying to bias a Marshall head...I think it was a JCM Slash before they were superwonderful. I didn't know much about the stuff; still don't. When I picked up the chasis to turn the bias pot I layed my finger across the progs for the main power switch. Man, am I lucky it was on. Even with the blunted does of e- my finger was numb for a week.
Don't ask me how I learned to use the selector knob on a multi-meter...
 
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